Method of making an ozonizer electrode unit



March 12, 1963 F. HELD ETAL 3,031,215

' METHOD OF MAKING AN OZONIZER ELECTRODE UNIT Filed July 7, 1959Patented Mar. 12, 1963 3,081,215 WTH'QD 9F MAKING AN UZGNIZER ELECTRGDEUNlT Fritz Held, Foreh, Zurich, and Willi Maag, Zurich, Switzerland,assignors to Gesellschaft zur Forderung dcr Forschung an der Eidg.Techn. Hochschule, Zurich, Switzerland Filed July 7, 1959, Ser. No.825,551 Claims priority, application Austria .luly 24, 1958 3 Claims.(Ql. 156286) This invention relates to an apparatus for producing ozoneby a silent discharge of electricity between a plurality of fiat,plate-shaped electrodes which are arranged in spaced juxtaposedrelation, alternately connected to opposite poles of a source of highvoltage and attached to dielectric plates which project roundabout overthe edges of the electrodes.

Such so-called plate ozonizers are known per se and have, as comparedwith tube ozonizers in which the electrodes are formed by coaxial tubesdisposed within each other, the advantage that they require less spacefor a given total electrode surface, thus rendering possible themanufacture of comparatively small apparatus.

A great problem in apparatus for producing ozone by a silent electricdischarge is the corrosion of the electrodes, especially when the air tobe ozonized is predried only partially or not at all. Although the yieldof ozone with dried air is greater, for technical use apparatus aredemanded whose efi'lciency is somewhat lower, but on the other hand donot require the costly additional appliances for drying the air and theattention on these appliances. Suoh ozonizers are particulary suitablefor temporary operation in small waterworks, industrial concerns and formobile plants, say, in the army. The ozone produced is mainly utilizedfor sterilizing water.

In order to avoid corrosion of the electrodes, corrosionand glow-proofdielectrics have already been interposed between the electrodes and thedischarge space, to thus keep away from the electrodes any aggressivesubstances in the'discharge space. But also the air, possibly presentbetween the dielectrics and the electrodes, may lead to corrosion of theelectrodes, since a glow discharge occurs there also.

In order to avoid any corrosion of the electrodes, the inventioncontemplates embedding each electrode between two dielectric plates, andfilling the space completely between these plates and between them andthe embedded electrodes with an adhesive binder, to be thus free fromair. In addition, through the adhesive binder the two dielectric platesand the intermediate electrodes are united to a coherent plate-shapedstructural element.

The above and other advantageous features of the invention willhereinafter more fully appear from the description, the claims and theaccompanying drawing, wherein there are shown purely by way of exampleone preferred embodiment and two modified forms of the object ofinvention.

In said annexed drawing:

FIG. 1 shows diagrammatically a sectional viewof an apparatus with aplurality of plate-shaped electrodes, taken on the line II of FIG. 2;

FIG. 2 shows a section of the same apparatus, taken on the line IIH ofFIG. 1;

FIG. 3 shows on a larger scale a structural element of the apparatuswith a single electrode as viewed from left to right in FIGS. 1 and 2;

FIG. 4 is a cross-section taken on the line IVIV of FIG. 3, on a largerscale;

FIG. 5 shows a fragmentary View of a modified form of the structuralelement in a representation similar to FIG. 3;

FIG. 6 is a cross-section taken on the line VIVI of FIG. 5, on a largerscale;

FIG. 7 shows a fragmentary view of another modified form of thestructural element, likewise in representation similar to FIG. 3.

The apparatus shown in FIGS. 1 and 2 comprises a casing 1t) whichpreferably consists of some corrosionproof synthetic material. Two walls11 opposite each other of the casing 10 are broken through and joinedwith connecting parts 12, into each of which a pipe 13 opensrespectively for supplying the air to be ozonized and for carrying offthe air enriched with ozone.

The casing 10 has arranged in it a plurality of plateshaped structuralelements 15 in spaced juxtaposed relation. Although each of saidelements 15 is composed of several parts which, however, constitute acoherent structural unit as explained further below, for the sake ofclarity FIGS. 1 and 2 show each the elements 15 as a single part only.On their inner sides the casing walls 11 have grooves which are engagedby the elements 15, as clearly shown in FIG. 2. The elements 15 areretained in their proper position by the ribs formed between saidgrooves.

FIGS. 3 and 4 show one of the elements 15 on a larger scale. Itcomprises two plates 16 and 17 of dielectric material, preferably glass,having embedded therebetween a flat, plate-shaped electrode 18. Theplates 16, 17 and the electrode 18 are connected to each other by anadhesive binder 18 which is also dielectric and completely fills thespace between the plates 16, 17 and between them and the electrode 18 sothat the space is free from air. Alternatively, instead of glass, theplates 16, 17 may consist of mica or ceramic material or some organicsynthetic substance. In the form according to FIGS. 3 and 4, theelectrode 18 is a metal foil, especially of aluminum. The electrode 18has formed on it an integral connecting lug 20 which projects beyond theedge of the plates 16, 17 and has a slit 21. The two dielectric plates16, 17 are larger than the electrode 18, and the plates 16, 17 projectroundabout at least 10 mm. beyond the edges of the electrode 18,preferably 20-30 mm, depending on the voltage of the source of highpotential used for producing the ozone. As an adhesive binder 19, apolymer synthetic substance, especially .polyvinyl acetate, is suitable.As will be seen in FIG. 3, the metal foil electrode is visible throughone sheet of glass and one layer of binder, both of which aretransparent.

The described elements 15 which among each other are all of identicaldesign, are so positioned in the casing 16 that the connecting lugs Zllof the successive elements 15 alternately project upwards and downwards,as shown in PEG. 1. All upwardly projecting lugs Zil are clamped betweenmetallic spacer sleeves 212 through which a threaded bar 23 is passed.Said bar is supported in the walls of the casing 1d and secured by meansof nuts 24. An additional nut 25 serves for clamping the spacer sleeves22 together with the lugs zit-engaging therein. In an entirely similarway, the downwardly projecting connecting lugs Ztl of the elements 15are clamped between metallic spacer sleeves 26, through which passes athreaded bar 27 which is supported in the casing 16 and secured by meansof nuts 28. An additional nut 29 on the bar 27 serves for clamping thespacer sleeves 26 together with the connecting lugs 20 engagingtherebetween.

The metallic threaded bars 23, 27 are connected to one end or the otherof the secondary winding of a highvoltage transformer 30 serving as asource of high voltage. In this way, the electrodes 18 arranged inspaced juxtaposition are alternately connected to opposite poles of thesource of high voltage 30.

The action of the described apparatus is as follows:

The air to be ozonized is blown into the casing through one of the pipes13, and then passed through the interspaces between the elements 15,where a silent electric discharge, a so-called glow-discharge, takesplace, whereby ozone is formed. The AC. voltage applied to theelectrodes 18 amounts to between 6,000 and 20,000 volts. The ozoneenriched with air is permitted to escape at the other side of the casing10 through the pipe 13 connected there. The dielectric plates 16, 17 andthe binder 19 of each structural element prevent the substances presentWithin the discharge space from reaching the electrodes 18 so as toprotect them from corrosion, V

which otherwise would occur owing to the generated aggressive gases,such as ozone, various oxides of nitrogen and nitric acid. Consequently,the described apparatus is also suitable for operation with air that isnot or only incompletely predried. Furthermore, the binder 19 and theplates 16, 17 will prevent the metal of the electrodes 18 from beingatomized through the glow-discharges on the surface thereof, wherebyalso the formation of electrically conductive layers of precipitate uponthe dielectric plates 16, 17 will be prevented. Only the component partslocated in the glow-zone, i.e. adjacent the discharge space are known tobe endangered by corrosion, for which reason the connecting lugs 20,spacer sleeves 22, 26, threaded bars 23, 27 and nuts 25, 29 locatedsubstantially outside the discharge space will be much less subject tocorrosion.

It is of advantage to have the dielectric plates 16, 17 of each element15 made of an inorganic material, inasmuch as, for instance, organicsynthetic substances, are indeed corrosion-proof, but less capable ofwithstanding the stresses caused by the electric glow-discharge. Thebinder 19 of the elements 15 may, however, without disadvantage, be anorganic synthetic substance, as it will be protected by the dielectricplates 16, 17 against the harmful influences of the glow-discharge.

The structural element 15 may, for instance, be manufactured as follows:

On a support (not shown) a glass plate 16 is first laid which, dependingon its size, may be 1-5 mm. thick. Then said plate 16 is covered with afoil 0.25-1 mm. thick, which mainly consists of polyvinyl acetate andincludes softeners, such as tricresyl phosphate. Subsequently, on saidfoil the metal electrode 18 is laid, which may be, for instance, 0.1-0.3mm. thick. Following this, a second foil of polyvinyl acetate is laidover the electrode 18, and thereupon the whole is covered with a secondglass plate 17. By evacuation, any air possibly present betweensaid'parts is drawn 01f, whereupon the composite body is heated in anautoclave and pressed together by means of a pressure gas. While beingheated, the polyvinyl acetate foils become plastic and intimately boundto the plates 16, 1'7 and electrode 18. Thereby the portions of thesynthetic foils immediately overlying each other outside the edges ofthe electrode weld together. Finally, the composite body is allowed tocool, and the synthetic substance, which possibly has come out betweenthe plates 16, 17, is cut ofi. The electrode 18, plates 16, 17 and thesynthetic substance 19 serving as an adhesive binder, now constitute thecohering, practically inseparable structural element 15 which can beconveniently built into the casing 10.

In FIGS. 5 and 6 there is shown a modified form of a structural element115. It is distinguished from the described elements 15 in that theelectrode 118 is not a metal foil, but a covering, say, a metallic layeror a non-metallic electrically conducting layer, applied to onedielectric plate. The layer 113 may be applied in a manner known per se,by spraying-on, depositing by vaporization, depositing from a solution,etc., whereby the layer may be given any desired shape by making use ofsuitable templates or the like. In the manufacture of the element 115,only a single plastic foil of, say, polyvinyl acetate, may be placedbetween the plate 17 provided with the layer, and the other plate 16,whereafter the procedure is the same as described with reference to thestructural element 15. After heating and pressing, the plastic foilforms an adhesive binding layer 119 between the plates 16, 17, in orderto connect them to each other practically inseparable. For connectingthe electrode 118 to the source of high voltage, according to FIG. 5there is provided a connecting lug 120 consisting of a thin metal foiland which, prior to the bonding of the two plates 16, 17, is connectedelectrically conductively with one end to the layer 118 and with itsother end allowed to protrude beyond one edge of the plate.

The second modified form of a structural element 215 shown in FIG. 7 isonly distinguished from the described elements 15 in that the electrode218 consists, instead of a metal foil, of a metallic netting or fabric.Instead of a connecting lug 20, some wires 220 of the netting 218project beyond the dielectric plates 16, 17. In making the element 215,the netting 218 is embedded, just like,

the electrode 18, between two plastic foils and between the dielectricplates 16, 17.

The principal advantage of the described apparatus for producing ozoneresults from the plate-shaped elements 15, or 215, which may be producedin any desired form and shape according to the particular use, andarranged side-by-side in any desired number. No special difiiculties areencountered in giving the structural elements the required mechanicaland thermal strength and in incorporating them afterwards in theapparatus. The described structural elements permit of operating theapparatus, if desired, also wit-h air dried incompletely or not at all.Moreover, it is of special importance that the elements '15, 115 or 2 15enable the construction of comparatively small apparatus, in whichwithin a given space, 'a relatively large total surface of electrodesmay be installed.

What we claim is:

1. Method of making an electrode unit for an apparatus for producingozone by a silent electric discharge between a plurality of fiatplate-shaped electrodes, consisting essentially of the following steps:assembling two films of transparent organic thermoplastic dielectricmaterial between two transparent dielectric glass plates and a smallerlayer of conductive metal, to serve as electrode, between said films,evacuating air from between films and plates and from between films andelectrodes, converting said film's into a plastically soft condition by'heating the assembly while simultaneously pressing the assembly, andfinally allowing the assembly to cool.

2. Method of making an electrode unit for an apparatus for producingozone by a silent electric discharge between a plurality of flatplate-like electrodes, consisting essentially of the following steps:depositing an electrically conducting metal layer, serving as anelectrode, onto one side of a first transparent dielectric glass plate,said electrode being smaller than said glass plate, assembling a film oftransparent organic thermoplastic dielectric material between saidelectrode-coated side of said first glass plate and a second transparentdielectric glass plate, evacuating air from between film and plates andfrom between film and electrode, converting said film into a plasticallysoft condition by heating the assembly While simultaneously pressing theassembly, and finally allowing the assembly to cool.

3. Method as defined in claim 1, in which the two 5 6 films oftransparent organic lthermoplastic dielectric rna- 2,136,572 WinkelmannNov. 15, 1938 terial are films of polyvinyl acetate. 2,403,241 SchaeferJuly 2, 1946 References Cited in the file of this patent 2744865 PennmgMay 1956 2,945,976 Fridrich et a1 July 19, 1960 UNITED STATES PATENTS 51,396,222 Lindemann Nov. 8, 1921 FOREIGN PATENTS 2,088,776 Dennison Aug,3, 1937 467,428 Great Brita-in June 16, 1937

1. METHOD OF MAKING AN ELECTRODE UNIT FOR AN APPARATUS FOR PRODUCINGOZONE BY A SILENT ELECTRIC DISCHARGE BETWEEN A PLURALITY OF FLATPLATE-SHAPED ELECTRODES, CONSISTING ESSENTIALLY OF THE FOLLOWING STEPS:ASSEMBLING TWO FILMS OF TRANSPARENT ORGANIC THERMOPLASTIC DIELECTRICMATERIAL BETWEEN TWO TRANSPARENT DIELECTRIC GLASS PLATES AND A SMALLERLAYER OF CONDCTIVE METAL, TO SERVE AS ELECTRODE, BETWEEN SAID FILMS,EVACUATING AIR FORM BETWEEN FILMS AND PLATES AND FROM BETWEEN FILMS ANDELECTRODES, CONVERTING SAID FILMS INTO A PLASTICALLY SOFT CONDITION BYHEATING THE ASSEMBLY WHILE SIMULTANEOUSLY PRESSING THE ASSEMBLY ANDFINALLY ALLOWING THE ASSEMBLY TO COOL.